Drill bit and fastening means



SePt- 1.5 1964 R. H. HoL'slNG 3,148,741

DRILL BIT AND FASTENING MEANS Filed Dec. 8. 1960 United States Patent O 3,143,741 DRILL BlT AND FASTENING NEANS Robert H. Helsing, Canton, Ohio, assigner to The Timken Roller Bearing Company, Canton, Ohio, a corporation of Ghio Filed Dec. 8, 1960, Ser. No. 74,533 1 Claim. (Cl. 175-413) The present invention relates to drill bits of the type in which a plurality of cutting pins are removably retained on the face of a bit holder. The present invention further relates to a novel means of positively retaining the bits in the bit holder.

It is an object of the present invention to provide a drill bit including a bit holder, a plurality of cutting pins, and means of positively retaining the cutting pins in the bit holder.

A further object is to provide a bit having a plurality of smaller cutting bits with abutting shoulders adjacent to the cutting face thereof and a spring pin inserted through a bit holder to engage grooves in the Shanks of the cutting inserts whereby the bits are positively held in a xed position in the bit holder.

Among the advantages achieved by the present invention are that each individual cutting bit can be rotated on its own axis to obtain a new gauge cutting edge without affecting any other bit in the group. Also, the abutting shoulders on the cutting bits keep the bits from turning when the drill is used, thus keeping the gauge diameter of the hole more accurate. Usable parts from a damaged bit assembly can be reused in another bit assembly so that all of the parts are used for their full life. The positive connection between the pin Shanks and the bit holder retain the bit in the bit holder so that individual cutting bits are not lost during a drilling operation.

These and other objects and advantages will become apparent hereinafter.

The present invention comprises a cluster bit including a plurality of cutting bits positively retained in a bit holder with engaged shoulders preventing relative rotative movement therebetween. The invention further consists in the parts and combinations and arrangements of parts hereinafter described and claimed.

In the accompanying drawings which form part of the specification and wherein like symbols refer to like parts wherever they occur:

FIG. 1 is an end elevational view of the present invention;

FIG. 2 is a sectional view taken along the line 2-2 of FIG. l; and

FIG. 3 is a side elevational View of a modified form of fastening means.

The present invention embodies a drill bit including a bit holder 11 whose shank portion is adapted to engage a drill rod (not shown). The bit holder 11 has a forward face 12 which is provided with a plurality of pockets 13. Each pocket 13 opens to the bit holder face 12 and has vertical side walls 14 terminating in a base 15. Extending laterally through each bit holder 11 from side to side are a pair of passageways 16 which engage the inner side Walls 14 of the sockets 13. The openings 16 define a semicircular groove 17 in each pocket side wall 14.

Each of the cutting bits 18 comprises a head portion 19 having a cutting face 20 provided with slots 21 wherein cutting inserts 22 are retained. The bit head portion 19 has iiattened sides 23 connecting the cutting face 20' and an opposed shoulder 24. A shank portion 25 having vertical side walls 26 terminating in a small butt end 2'7 is connected to the head portion 19 at the shoulder 24. The shank portion 25 is provided with a necked down portion or groove 28 which is adapted to correspond to the groove 17 in the bit holder pocket 13 when the cutting bit 13 is received in the socket 13.

A fastening means 29, such as the illustrated rolled metal pin, is inserted into the bit holder passageway 16 and engages the groove 17 in the pocket side wall 14 and also engages the groove 28 in the shank 25. In the embodiment shown, the fastening means 29 is of a larger diameter than the passageway 16 and is compressed slightly when inserted into said passageway. Therefore, the diameter of the fastening means must be variable.

When the pin 29 is inserted into the passageway 16, it is compressed as hereinbefore explained. Thus, the outward pressure which it exerts against the inner surface of the passageway 16 retains the pin 29 in the passageway 16. The pin 29 also engages the necked down portion 28 of the bit shank 25 to positively retain said bit 18 in the bit holder pocket 13. The bit 18 cannot be removed from the bit holder 11 until the pressure pin 29 is withdrawn from its active position connecting the grooves 17 and 23 in the pocket side wall 14 and the bit shank 25 respectively. FIG. 3 shows a modified form of fastening means which is a pin 3) having tapered ends 31 and a lengthwise slot 32 therein. The outside diameter of the pin 36 is larger than the passageway 16 so that the pin is compressed when it is forced into said passageway 16.

When the cluster bit 10 is in use, two flattened sides 23 of each cutting bit 18 abut against corresponding sides 23 on the other bits 18, thus preventing relative rotation between the bits 18. The bit head shoulder 24 does not touch the bit holder front face 12, while the bit shank butt end 27 is received on the bottom 15 of the pocket 13 in the bit holder 11. Fluid passages can be provided to the front face 12 of the pin holder 11 so that fluid or air can be forced into the cutting area to carry the rock chips away from the cutting area.

It is intended that either carbide or all steel bits can be used in this construction. Either single edge bits, commonly known as chisel bits, or multiple edge bits are suitable for use in the present invention. The outer periphery of the cutting area or cutting face 20 is defined by the outermost edges of the cutting inserts 22, and must be greater than the outer periphery of the bit holder 11 to drill a clear hole which will hold the cluster bit 10.

'Ihe small cutting bits 18 must be grouped radially in the bit holder 11 rather than in a single or double line. Radially grouped bits provide more speed when drilling because of the better coverage, and increase the life of the bit. The large number of cutting edges provided by the cluster bit construction of the present invention also adds to the life of the bit and to the speed of drilling. The present cluster bit provides more uniformly smaller chips when drilling, and these chips are more easily moved from the hole than large uneven chips. When the portion of a bit insert that defines the gauge diameter of the hole becomes worn, it is not necessary to discard the bit, since it can merely be turned a quarter turn and a new insert is presented to the gauge diameter. This is of considerable importance, since it increases the life of the bit at least fourfold, besides giving a more constant gauge diameter and a more constant degree of sharpness to the cutting face.

If desired, the bit holder 11 can be made of a special material and heat treated to stand excessive hammering blows, while the bits 1S can be made from material suitable for brazing or otherwise attaching the cutting inserts 22.

When the pressure pin retaining means 29 is used, it is not necessary to seat the inset bits 18 in their sockets 13 by driving before drilling, nor is it necessary to be sure that the air hammer is not operated until it reaches the bottom of the hole. The pressure pins 29 stay in tight, do not rotate during drilling and do not tend to work out of the holes.

Thus it is apparent that the present invention provides a novel drill bit including a bit holder retaining cutting bits having abutting shoulders to restrain rotation between the cutting bits, and a positive pressure pin lock means which retains the cutting bits in the bit holder.

This invention is intended to cover all changes and modiications of the examples of the invention herein chosen for purposes of disclosure which do not constitute departures from the spirit and scope of the invention.

What is claimed is:

A drill bit comprising a drill bit holder provided with four open ended straight walled sockets and two open ended transverse passageways, each of said passageways intersecting two of said sockets, four cutting bits comprising head portions having slots therein and shank portions adapted to be received in the sockets, cutter inserts positioned in said slots defining a cutting area whose outer periphery deiines the gauge diameter of the bit, flattened side Walls on each bit head portion adapted to engage a correspondingly attened portion on an adjacent bit to retain the cutting bits xed in the bit holder relative to each other, each of the cutting bit shank portions having a notch aligned with the intersection of one of the trans verse passageways and the bit holder socket, and fastening pin means positioned in each of the transverse slots, each of said pin means engaging both the bit holder and two of the bit shank notches to positively retain the bits in their sockets, each of said fastening pin means being of a larger diameter than the bit holder passageways and the shank notches and being compressible to lit tightly in said passageways and said notches, said pin exerting an outward pressure on the inner surfaces of said passageways and on the shank notch surfaces to retain the Shanks securely in said sockets.

References Cited in the le of this patent UNITED STATES PATENTS 63,681 White Apr. 9, 1867 1,423,713 Des Roches July 25, 1922 1,589,596 Holianson June 22, 1926 1,762,504 Bull June 10, 1930 1,874,066 Scott et al Aug. 30, 1932 2,049,543 Kammerer Aug. 4, 1936 2,203,216 Hokanson June 4, 1940 2,215,948 Williams Sept, 24, 1940 2,506,387 Ross May 2, 1950 2,716,822 Launder et al Sept. 6, 1955 2,737,843 Koehl Mar. 13, 1956 3,075,593 Holsing Jan. 29, 1963 OTHER REFERENCES Ser. No. 384,737, Meutsch (A.P.C.), published May 25, 1943. 

